Anatomy of a Human Heart
by Best Damn Avocado
Summary: Sherlock Holmes is tired of heaven's politics but a new challenge set in his path by none other than Mycroft Holmes has the potential to change things forever. Angel AU.
1. Chapter 1

**NOTE:** This fic is a gift for the beautiful Grace, whose friendship and talented writing have been some of the best gifts I've ever had the privilege of receiving. Merry Christmas!

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Mycroft Holmes stood on a jagged cliff in Afghanistan, watching a dusty skirmish unfold in the distance. His countenance bore the detached indifference that was common to his kind—the sort of indifference that came with centuries of watching humans slaughtering each other in increasingly creative ways. Human nature no longer surprised him. His job, however, as with the job of every other angel in existence, was not to intervene with human history but to protect God's creation from demonic influence and harm.

His current appointed task was conducive towards that goal. Whispers of a powerful demon weaving trouble like a spider web over the whole of Earth had reached heavenly ears. His network was vast by all accounts. Whoever was assigned the mission would be spending quite a bit of time stationed on Earth—London, specifically—with the possibility of a permanent stay. Mycroft already had an angel in mind.

"Have you told Sherlock?" Naomi, the angel standing beside him in regal silence, spoke with her usual musicality. "You're to be brothers again for this operation."

"I've told him," Mycroft confirmed. "He enjoys the cover story. It means he can be his usual irreverent self and I have to hold my tongue."

"When do you ever hold your tongue? I rather think you enjoy the cover yourself," she retorted without looking his way. "You're attached to him, are you not? You have been since his creation."

Mycroft didn't need to confirm for her to know she was right. Superior intellect was one of the many things they had in common. Very little escaped her notice. He'd often thought perhaps that was the reason their connection was so harmonious and balanced. They were two of a kind.

"What of Natalia?" He prompted after a short pause. In the distance events were quickly coming to a close. He could hear voices and gunfire, but he was zeroed in on one particular blonde-haired human with considerable promise. He was skidding next to a downed soldier and kneeling to put pressure on a bullet wound. John Watson would do nicely for his purposes.

"I've cleared her schedule per your request and have informed her she is to be at your disposal. Your covers have already been established as well. I implanted the necessary memories in strategically chosen humans myself. Sherlock is to be a consulting detective and you, his brother, are to work for the government. Living arrangements are still pending." Naomi lapsed into thoughtful silence. "Are you concerned?"

"No more than usual. It's not the first time we've dealt with a threat of this magnitude."

"Then I'm confident the mission will be fulfilled to everyone's satisfaction," Naomi replied with the faintest of smiles. "Is it time? You've yet to let me in on the details."

Mycroft squinted his eyes the moment John Watson's shoulder was torn through with a bullet, and nodded once in reply. "I will in a moment," he assured her.

Together they flew straight into the sandy warzone, wings outstretched in their entire heavenly splendor. Mycroft was especially fond of Naomi's, their luminescent gray so incredibly soft to the touch. He brushed the memory aside to kneel beside the downed body of John Watson, seeping copious amounts of blood into the sand beneath already.

"Please, God, let me live," John breathed.

Mycroft put two fingers to his forehead while Naomi stood with her eyes closed, sensing the nearest military checkpoint. "John Hamish Watson, it is not yet your time to die," he spoke quietly.

"I've found it," she informed him. "Help is already on the way. Are you ready?"

"Just a moment." Mycroft nudged John into unconsciousness and slowed his bleeding, making sure to leave as little evidence of his tampering as possible. He stood when he was finished and after only a subtle nod of his head, flew back to their perch atop the cliff.

The silence stretched between them until eventually Mycroft saw fit to speak. "Sherlock is tired of the political battles in heaven," he explained. "They hold no interest for him. He's bored and he... struggles."

"He's become destructive," Naomi concluded solemnly.

"Yes," Mycroft confirmed at length. "He needs a challenge. Something that'll engage the full spectrum of his talents."

"And you are going to create one for him?"

"Earth has no shortage of demonic challenges already, I'm simply placing one of them in his path," he said. "It should keep him busy. And if all goes according to plan his stay on Earth will be permanent."

Naomi turned bright blue eyes his way, keen and observant. "What of the human?"

"A counterweight of sorts," he further explained. "I've been watching him a long time to make sure he's a proper fit."

Naomi's tone came through as curious and faintly amused. "You've found Sherlock a friend?"

"Well," Mycroft hesitated, "yes, I suppose I have. A temporary one, at least."

He turned to meet her eyes and between them there was the pure and untainted understanding of two beings bound to each other in ways very few could comprehend. Humans would call them soul mates but such a concept, by the very smallness of its definition, did not apply. Naomi's fingers grazed his cheek and he closed his eyes.

"You never fail to surprise me," she said softly.

"You know better than anyone that my reputation as the 'Ice Man' only goes so far." He reopened his eyes and she withdrew her hand, once again unreadable and composed. He smoothed the front of three-piece suit. "Shall we?"

And with a flutter of feathers, they left little more than dusty tendrils in their wake.


	2. Chapter 2

Several months later, Sherlock was already on the demon's scent. He'd chased it like a bloodhound through every case that fell on his doorstep, until the mind-numbing boredom that came with the politics of heaven was long forgotten. He felt more like himself than he had in centuries.

John Watson had proved himself a valuable part of his human cover thus far. He was quick, decisive and more than equal to the task. Sherlock found his steadfast loyalty intriguing and his ability as a sounding board useful. He was his conductor of light—and together they worked _wonders_.

Mycroft had seen their growing camaraderie during his occasional visits and warned Sherlock against becoming too involved. Even if he succeeded in his mission and was permanently assigned to Earth, John was still human. He would always grow old or sick, and die, as all humans did. The pain of loss was all too familiar.

Centuries previous Mycroft Holmes had grown attached to a human himself. His very own 'John Watson' until the brittle hand of old age took hold of him. Mycroft stayed by his friend's bedside to the bitter end, but angelic emotions run deep and the sorrow provoked by his loss proved too great. Sherlock and Naomi were the sole recipients of his affections now.

Sherlock didn't heed the warning. He rarely did. Mycroft hadn't been able to save his friend but he was a better angel for it in the end. Sherlock could already feel himself changing through his continued interactions with John.

He was playing a dangerous game though. The demon he'd been chasing for months had identified John Watson as a weakness. He'd strapped him to a bomb and paraded the frailty of his humanity in front of him. Angels were powerful but they had limits. Sherlock had been on the verge of having to choose between salvaging his mission and saving his friend. In the end Moriarty had revealed a weakness of his own. His search for meaning and validation, in life as in death. Sherlock tucked the information away to use against him, but the flush of a waiting challenge followed him all the way back to the flat.

"I'm going to turn in," John announced with a heavy sigh once they crossed the threshold into 221B. "Much as I'd like to drink until I pass out and forget tonight ever happened," he yanked his coat off, "I'm worn out."

"You very nearly lost your life this evening. I'm sure you could use the rest." Sherlock settled into his chair without removing his coat and pressed his joined hands to his lips, blue eyes darting over his new flat mate.

John gave him a bit of a look. "I wasn't the only one who very nearly lost my life. You're not immortal, you know."

"You'd be surprised." Sherlock's wings twitched amusement, even though John couldn't see. "I'll see you tomorrow."

"Get some sleep!" John called on his way up to his room.

Sherlock watched him disappear up the stairs before settling his hands on the armrests of his chair, long fingers fidgeting anxiously. He wasn't sure how long he sat in silent contemplation of his new friend before the subtlest flutter of wings drew his attention to the chair in front of him, and the petite figure perched on its back.

"Is that a smile I spy on your face? I think it's been centuries," Natalia teased in greeting.

Sherlock's eyes swept over her. He'd seen her take various human vessels over the years but he was convinced this one suited her best, with its glossy red waves, pale alabaster skin and luminous green eyes. _A great and terrible beauty._ Hers was one half of a pair of lovers whose bloodlines made them both potential angelic hosts. Sherlock's vessel was her counterpart.

They'd discovered the unusual couple in 19th century London during the Victorian Era. Sherlock had questioned the chances of encountering a pair of potential vessels so intimately entwined and yet genetically unrelated. "Slim," had been Natalia's reply. "But we thrive on slim chances, don't we?"

He pulled his thoughts back into the present to find she'd settled properly into the chair. Her shapely legs had been thrown over one armrest and her large crimson wings over the other. "Mycroft sent me over," she continued. "He said you might have information for me to follow up on."

"A name," Sherlock confirmed. "Moriarty. It's what the demon's calling himself these days. I need you to look into his connections," he explained. "He's been dealing mostly with humans but I suspect his network is vaster than that."

"I'll see what I can dig up." Natasha's smile was soft but her expression was otherwise unreadable. "How are you?"

His wings fidgeted softly behind him. "Humans try my patience on a daily basis but it's a far cry from the dullness of heaven."

"I suppose anything's better than politics," she quipped.

"Don't tell Mycroft."

"Naomi has eyes and ear everywhere. He probably knows already," she retorted in deadpan humor. "You know political whispers are referring to them as our King and Queen?"

"Are they? And how goes their reign? I prod him for information but he rarely gives anything away."

"It's going." Natalia slipped out of her chair to walk round the room as if she'd suddenly recognized the location for what it was. Locations inevitably blurred into an unrecognizable mass of four-walled rooms after centuries of missions and covers, but this one was different. This one had _history_. "Naomi's not big on sharing details either, but they seem to have things well in hand." She turned to him with a vague gesture at their surroundings. "Was it your choice to live here?"

"Yes," he said simply.

Natalia dropped her hand and blinked at him. "You remember this was where we—"

"Why do you think I chose it? If there's even the slightest chance I'm going to stay here permanently I'm claiming this place as mine." He met her stare for stare.

"You always were possessive." Natalia turned to study the room one more time. "I thought maybe you'd deleted the details."

"They were details worth keeping." He clasped his hands on his lap and she walked back over to take a seat on the armrest. He lowered his eyes to his hands. "And I rarely delete details when they concern you. I thought you knew that," he finished quietly.

Natalia's lips lifted at the corner. "I only pretend I know everything, Sherlock."

Their eyes met and for a moment it could've been 1892. Back then they'd only recently acquired their vessels and had grown curious about their memories as a couple—the odd intensity of physical affection. Angels didn't experience those urges first hand the way humans did, but for one night Sherlock and Natalia experimented similarly themselves. The experience had been enjoyable and rewarding in many ways.

Sherlock tucked the memory away and cleared his throat. "You'll let me know the moment you find anything on Moriarty?"

"Shouldn't be more than a day or two," Natalia promised and leaned in to kiss his cheek. Sherlock's velvety black wings brushed tenderly against hers. "Stay out of trouble," she finished quietly.

And before he could reply, she spread her wings and disappeared.


	3. Chapter 3

Despite Sherlock's progress on Earth, things in heaven were taking a dark turn. Naomi's position as head of heaven's intelligence division afforded her unique insight into the underbelly of angelical plotting and scheming. Her sources reported Moriarty's name had been cropping up frequently in half whispers and backroom deals. Sherlock's suspicions of a network that spanned beyond the confines of Earth had been confirmed. Moriarty's demonic influence was snaking its way up angelical ranks.

Mycroft apprehended him shortly after the incident with Irene Adler, but Moriarty refused to speak. He'd even taken measures to protect the information inside his head from Naomi's particular brand of extraction. Moriarty proposed a deal: information about Sherlock in exchange for information about his network. Mycroft got all he could out of him before he was forced to let him go. The walls of his cell had been riddled with Sherlock's name.

His position in heaven was now precarious. Moriarty's followers were hungry for power and angels who opposed him were turning up dead left and right. The circle of people Mycroft could trust had grown smaller and smaller and his life had been in peril more than once already.

"We need to do something," Naomi told him grimly after a particularly close call. Her eyes glowed a brilliant gold that matched the energy radiating from her hand already healing his wounds. He tipped his head against the back of her chair and closed his eyes. "If Anthea was even a second late in calling me, you could've—"

"I am _fine_ , Naomi," he said soothingly.

"You're fine this time," she conceded, "but what about the next? You can't keep Sherlock in the dark any longer. It's time to let him know."

Mycroft opened his eyes to find Naomi's gaze had gone back to its usual fierce blue. Wavy auburn tendrils escaped her bun and framed her face. He reached out to tuck one back behind her ear. "Very well," he finally spoke. "We tell him today but we keep this little incident between ourselves."

"Then you need to stop touching me so I can finish healing you. I can't concentrate," Naomi told him with an almost indulgent smile before resuming her ministrations.

They found Sherlock in St. Bart's Hospital. Molly Hooper stood a little ways behind him in a plastic cover up, jotting down copious notes. Sherlock hadn't bothered with the cover up. His light blue shirt and black trousers were streaked with blood already.

" _Brother dear_ ," he spoke formally when Mycroft and Naomi entered the morgue. He rested the harpoon he'd been using on the floor and eyed his new visitors with a calculating eye. "Molly, coffee," he spoke after a short pause.

"What? _Now_?" Molly dubiously darted her eyes between Mycroft, Naomi and Sherlock.

"Yes, now." He flashed her a charming smile. "If you don't mind? You're the only one who knows how I like it."

Molly returned the smiled but hesitated before setting her clipboard down. "Okay, just don't do... anything until I get back. I'm already going to get sacked for this if anyone finds out." Her cover-up came off and she headed for the door. "I'll be right back."

"I'm working. What do you want?" Sherlock spoke once Molly was out of earshot.

Mycroft eyed the corpse and bloody mess for a moment. "You remember I told you we had Moriarty in custody recently?"

"Yes, and you told me about your little deal." Sherlock settled his free hand on his hip and his wings pulled close to his back. "Was it worth the trouble?"

"We fed him the necessary information. It's up to him if he wants to use it," Naomi answered professionally. "We have another situation on our hands now, however."

"We've confirmed Moriarty has followers amongst our ranks," Mycroft continued. "There've been six angel deaths within the last month already, and angel deaths are _rare_. The amount of people we can trust has been severely diminished."

Sherlock paced away while tapping the harpoon on the floor, then turned back. "What about Anthea?"

Mycroft nodded shortly. "Anthea, Naomi, Natalia and myself. That's the extent of our little circle."

"Four angels isn't much, but it's something," Sherlock said absently.

"You have a plan?" Naomi prompted.

"I have several I've been working on for a while," he confirmed. "Natalia's been looking into his connections for me. I suspected there might be angels amongst the members of his network and this confirms it." He ruffled his hair. "We'll need to work off the grid if we don't want him to catch wind of our plan."

Naomi and Mycroft exchanged a look but it was Mycroft who spoke. "What are you proposing?"

"Nothing yet. Let's see what he does with the information you gave him first. If my deductions are correct—"

"Here's that coffee you asked for," Molly chirped happily as she pushed her way back inside the morgue. Realizing she was interrupting something, she hesitated by the door. "Should I come back?"

"No," Mycroft said quickly. "We're done here. I'll be in touch, _little brother_."

Naomi followed him out the door and behind them there was an annoyed snap of wings. Presumably because of the 'little brother' jab. Mycroft's lips twitched into the briefest of smiles.

Having made sure the outside corridor was empty, Mycroft and Naomi disappeared to a safe house they'd set up in secret several decades previous: The Diogenes Club. The building was extensively protected against demons and angels alike.

Mycroft settled heavily into his desk chair and closed the door with a flick of his hand. Naomi perched near him on the edge of his desk and took her hair out of her bun, popping open the first two buttons of her shirt. Her silvery grey wings sagged tiredly behind her.

He moved his chair closer, no longer worried about propriety within the privacy of his office. The Diogenes Club was their sanctuary. He could shed his 'Ice Man' persona at the door and be himself. His fingers twined slowly with hers. "Are you all right?"

"You know I don't like politics," she answered quietly.

"Or being forced out of your office."

"That too." Naomi brought his hand to her lips and kissed his knuckles. "Will you hold me?"

"Always." Mycroft gathered in his arms and arranged his large golden wings in a circle around them. There was a chill in the air, like an _East Wind_ heading their way. He snaked an arm around her waist and pulled her close, quietly repeating his answer. "Always."


	4. Chapter 4

Things progressed quickly after Mycroft and Naomi's visit, with Moriarty's open display of power and his following trial. His acquittal came as no surprise. Human justice could do little to stop him. Moriarty was putting on a show.

His visit after the trial left Sherlock curled up on his bed an hour after his departure, large black wings drooping over the edge of the mattress and spilling to the floor. Moriarty's 'I.O.U.' stared at his back from the bedside table, crudely carved into an apple. John still hadn't returned from the courthouse.

Sherlock had narrowed down his theories and formulated a plan in his absence. Events were unfolding as planned but the most difficult part still lay ahead. He was close to figuring it out—the game, the 'I.O.U.'—but the closer he got to the answer, the more he feared for his new friend's life. He couldn't lose John. His connection to the human was difficult to explain in logical terms, but he'd grown attached to the warmth and constancy of his friendship. His _humaneness_. Mycroft warned him not to get attached. He made it clear that sooner or later, through death or duty, Sherlock would have to leave John behind and move on. With the fate of heaven and Earth hanging in the balance, fulfilling his mission was priority. Sherlock was clear.

And yet— _and yet_.

There was a flutter of wings and the slightest dip in the bed. Sherlock didn't have to open his eyes to know who'd joined him. Natalia was always quick to appear when his grace grew heavy with sorrow and this time was no different. Her hand was warm on his cheek when he opened his eyes.

"I didn't call for you," he said quietly.

"You didn't have to." She mirrored his position on the bed, long red hair streaking across the pillow like blood and warm green gaze steady on his blue one. Every inch of her spoke of fire, brimstone and death, and yet with him she was always soft and tender. Slowly she lifted one of her crimson wings and curved it protectively over his body, feathered tip gently grazing his ebony feathers. "Is it John?"

Sherlock's wings twitched involuntarily and he closed his eyes without immediate reply. Her thumb stroked his cheek. "I need you to look after him," he said at length.

"And who's going to look after you?"

"I've got a plan. Molly Hooper—" He swallowed hard. "Please, will you do this for me?"

"Always," Natalia answered without hesitation. "Whatever you need."

His voice was a soft rumble. "Thank you."

Natalia drew herself closer and Sherlock lifted one of his wings, tucking it intimately against the one she'd already curved over his body so that they were cocooned in a sort of feathery embrace. They'd learned physical affection from their vessels but they'd always found comfort in the warmth of each other's grace. Their wings were a mere extension.

Sherlock pressed his forehead against hers. "I wouldn't be able to forgive myself if anything happened to him. He's—"

"Special," Natalia finished for him. "Of course he is. He's your friend." Her hand moved from his cheek to his chest and she waited until he'd opened his eyes to speak again. "Nothing is going to happen to him, okay? You have my word. And whether it's months from now or years, you'll see him again."

"Assuming I succeed in—"

"You will," she interrupted.

His lips twitched faintly at the corner. "You don't even know my plan."

Natasha shrugged a shoulder and her wing moved pleasantly against his, like a gentle caress. "I know _you_. And that's all I need to know."

Sherlock took the hand on his chest and brought it back to his cheek. "You're very confident."

"I've got reason to be." Natalia resumed stroking his cheek with her thumb like she knew he wanted. Several heartbeats ticked by before John's footsteps could be heard racing up the stairs and a shouted 'Sherlock!' drifted through the closed door of his bedroom. Natalia leaned in like she had all the time in the world and brushed her lips against Sherlock's. "Call me if you need me," she requested.

By the time John opened the door, Sherlock was sitting up alone in bed. He pretended to scrub the sleep out of his eyes. "What time is it?"

"Were you _napping_?" John shot him an accusing glare. "Moriarty was found 'not guilty' and you're—"

"Working. Come along, John." Sherlock darted off the bed and grabbed his coat on his way out the door. "The game is on."


	5. Chapter 5

Events came to a head on the roof of London's St. Bart's Hospital. Sherlock had undergone many changes over the centuries but few as profound as the one he'd undergone during his friendship with John. His fierce compassion, unconditional acceptance and unfailing loyalty rid Sherlock of the destructive apathy he'd acquired during his extended stay in heaven.

That same heaven was now in shambles. Suspicion, fear and thirst for power had wreaked havoc on what should've been a well-oiled machine. Mycroft and Naomi had quite a lot of work ahead of them if they were to restore order, but Moriarty and his network had to be dealt with first. Sherlock would see to that himself.

Bolstered by his friendship with John and safe in the knowledge that Natalia would see to his well being in his absence, Sherlock sought Molly's help and put his elaborate plan in motion. He played to Moriarty's weaknesses and drove him to his death. He put on a show for the members of his network who would've killed his human friends. He watched John suffer his loss.

The road that stretched ahead of him was long and difficult with Moriarty's network still active and scattered despite his death, but the pain of hurting such a loyal friend cost him dearly. Sherlock vowed to make it right.

It took him two years and countless close calls. Mycroft and Naomi were busy righting wrongs in heaven, but Natalia helped when she wasn't busy keeping an eye on John. He took comfort in the knowledge that he was alive and safe. Natalia relayed the details of his life during their quieter moments together, wings twined in comfort. John's clinic. His first date with Mary. His visits to Sherlock's grave. The ever-growing mustache went conveniently unmentioned.

Sherlock didn't crave a human life for himself. He was an angel. He enjoyed tracking demons and untangling their meticulously built webs. Natalia's occasional visits and overnight stays were a welcome reprieve from the loneliness that came with such a job, but Sherlock still missed his friend.

Two years later he got a visit of a different sort. Mycroft smuggled his way through the ranks of his last mission and informed him of a new threat that required his attention. It was time to go home.

Natalia wore a black cocktail dress and a smile to meet him outside the restaurant John had chosen as the setting of his marriage proposal to Mary. "You clean up nicely," she quipped. "How does it feel to be Sherlock Holmes again?"

"I'm still missing one thing." Sherlock approached her with his hands in his coat pockets and they circled each other once, wings barely touching. His lips turned up at the corner. "I hear you're going by Natasha, nowadays."

"I'm always Natalia to you." She held his gaze. "He's right inside. Keep the dramatics to a minimum, will you?"

"Minimum? It wouldn't be my style," he quipped.

She smiled again. "I won't be able to guarantee your safety if you piss him off."

"When's a little risk ever stopped me before? It'll be fine." He winked and walked backwards towards the door, wings outstretched. "He'll be happy to see me."

Natalia laughed and stole a peek down the sidewalk before returning her eyes to his face. "Come find me afterwards. I'll fix your vessel for you."

"Oh, ye of little faith," he retorted dramatically.

Mycroft and Naomi joined her once Sherlock pushed his way inside the restaurant. "Shall we go watch the reunion, then? I did try to warn him but he so rarely listens to me," Mycroft said.

They all transported themselves inside the restaurant without further ceremony and made themselves invisible to human eyes. Sherlock already snaked his way through tables, building up his disguise on his way over to John. Naomi clasped her hands in front and looked on with a serene smile.

"I've been looking into Mary Morstan," she announced when the blonde ex-assassin made her appearance. "It seems John Watson's got a penchant for the dangerous and unusual. She's got quite an interesting history. "

Mycroft stole a peek at Naomi. "Does she now? I assume you'll be catching me up over a game of chess? I'm afraid I've only been keeping a weather eye on John."

"Is _chess_ what you kids are calling it these days?" Natalia teased but her eyes were still on John and Sherlock, and their tense reunion. When John attacked she turned to face Mycroft and Naomi with a barely there smile. "Well, have fun. I've got a feeling I'll be getting a call from a grumpy angel sometime in the near future and I've got something to take care of first." She winked and spread her wings, disappearing a moment later.

Mycroft sighed heavily and slipped his hands inside his trouser pockets. "Incorrigible."

"You say the same about Sherlock," Naomi observed.

"Well they're _both_ incorrigible."

"And yet," she added with a hint of teasing to her tone.

"And yet," he agreed and offered his hand. "Shall we, then? I was serious about that game of chess. It's been far too long."

They disappeared with a flutter of wings just as Sherlock retrieved his coat and shrugged it on. A fuming John followed close behind, with a concerned Mary in tow. The air outside was brisk. Like an _East Wind._

It wasn't a perfect reunion but it was the start of something new. An adventure. A friendship. A partnership for a lifetime. The game wasn't over yet—the game was _never_ over.

The game was only just beginning.


End file.
